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Define the term niche.
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Define the term niche.
A niche is the role of a species within its habitat.
What are some examples of factors that make up an organism's niche?
Examples of factors that make up an organism's niche include:
what it eats
which other species depend on it for food
what time of day it is active
exactly where in a habitat it lives
exactly where in a habitat it feeds
True or False?
Two species can occupy exactly the same niche within a habitat.
False.
No two species can fill the same niche within a habitat. When two species are in direct competition for the same niche one species will out-compete the other, causing it to die out in that particular habitat.
True or False?
Species can only survive in habitats in which they are well adapted to their niche.
True.
Species must be well adapted to fill their niche in order to survive in a habitat.
What are examples of biotic interactions that influence an organism's ability to fill its niche?
Examples of biotic interactions that influence an organism's ability to fill its niche include:
contact with pathogens and parasites
competition for food
avoiding predators
finding food
True or False?
All organisms can switch between aerobic and anaerobic respiration.
False.
Some organisms can switch between aerobic and anaerobic respiration while many survive using only one type of respiration.
Where can obligate anaerobes be found?
Obligate anaerobes can be found in oxygen-free environments such as:
lower layers of soil
deep water
inside the bodies of other organisms.
What are facultative anaerobes?
Facultative anaerobes are organisms that mainly respire aerobically but can switch to anaerobic respiration in the absence of oxygen without negative effects.
What are obligate aerobes?
Obligate aerobes are organisms that cannot survive in the absence of oxygen and rely on aerobic respiration to release energy from food.
What happens if obligate aerobes perform anaerobic respiration?
If obligate aerobes perform anaerobic respiration they will need to switch back to aerobic respiration after very short periods (a few seconds); this is due to damaging effects on cells.
What is meant by the phrase mode of nutrition?
An organism's mode of nutrition is the way in which it acquires organic molecules to fuel respiration.
How does photosynthesis function as a mode of nutrition?
Photosynthesis functions as a mode of nutrition by transferring light energy into a chemical form that can be used by living organisms.
What are the main types of photosynthetic organisms?
Photosynthetic organisms include:
plants
algae
photosynthetic bacteria, such as cyanobacteria
Define the term holozoic nutrition.
Holozoic nutrition is a form of heterotrophy where organisms ingest, internally digest, absorb, and assimilate organic molecules from the tissues of other organisms.
True or False?
All animals are heterotrophic.
True.
All animals gain their organic molecules from the tissues of other organisms, meaning that they are all heterotrophic.
What is a mixotroph?
A mixotroph is an organism that can use both autotrophic and heterotrophic methods of nutrition.
Give an example of a mixotrophic organism.
Euglena is a mixotroph that gains organic molecules both by photosynthesis and by ingesting and digesting bacterial cells.
What distinguishes obligate mixotrophs from facultative mixotrophs?
Obligate mixotrophs must constantly use both methods of nutrition, while facultative mixotrophs can survive on one method of nutrition, which may be supplemented by the other.
What are saprotrophs?
Saprotrophs are heterotrophs that digest food externally by secreting enzymes onto dead or waste material, then absorbing the digested products.
Name two examples of saprotrophic organisms.
Fungi and bacteria are common examples of saprotrophs.
What are the archaea?
The archaea are a group of single-celled organisms that make up one of the three domains.
What are some of the ways that archaea provide energy for ATP production?
Archaea can provide energy for ATP production from:
light (phototrophic)
oxidation of inorganic chemicals (chemotrophic)
oxidation of carbon compound (heterotrophic)
Chimps have relatively small jaw muscles while gorillas have very strong jaw muscles.
What does this suggest about the diets of the two species?
The following is suggested by the dentition of chimps and gorillas:
small jaw muscles in chimps = softer foods, e.g. meat and fruit
large jaw muscles in gorillas = tougher foods, e.g. plant material
True or False?
The dentition of extinct hominids can provide clues about their diet.
True.
The dentition seen in fossils from extinct hominids can provide clues about their diet.
Why do teeth not provide a perfect indication of the diets of extinct hominids?
Teeth do not provide a perfect picture of the diets of extinct hominids because eating would not have been the only role played by teeth; they may also have been involved with, e.g. defending territory.
What does the presence of large molars in Paranthropus robustus suggest about its diet?
The presence of large molars in Paranthropus robustus suggests a diet of tough plant material.
What kinds of fossil evidence from Homo floresiensis might suggest that they were primarily plant eaters, but that they may have eaten some meat?
Fossil evidence from Homo floresiensis that suggests information about their diet includes:
Primarily plant eaters:
large grinding teeth
large jaw
tooth abrasions visible under microscope
May have eaten some meat:
skull shape similar to modern humans
How is the use of fossil skulls to determine early hominid diet an example of deduction? (NOS)
The use of fossil skulls to determine early hominid diet is an example of deduction because the deductive process starts with a theory, from which hypotheses can be developed. In the example of hominid dentition:
There are theories about the relationship between dentition and diet that have been developed from studying living hominids
E.g. large molars = diet of vegetation
These theories can be used to develop hypotheses about the diets of extinct hominids
E.g. P. robustus had large grinding teeth, so therefore had a diet of vegetation
Define the term herbivore.
A herbivore is a heterotroph that feeds on plants.
How are some insect mouthparts adapted for herbivory?
Adaptations of insect mouthparts for herbivory include:
stylets that pierce plant tissue, e.g. in aphids
mandibles that cut through plant tissue by chewing, e.g. in caterpillars
What is an example of a mechanical defence against herbivory in plants?
Mechanical defences against herbivory in plants include:
cacti have sharp spines
nettles have tiny hairs that contain toxins
thick bark
hairy leaves
How do plants use secondary compounds as a defence against herbivory?
Plants may use secondary compounds as a chemical defence against herbivory as follows:
compounds such as digitalis, atropine and caffeine may be toxic
compounds such as tannins may taste bitter
How do some mammals avoid being harmed by toxins in the plants that they consume?
Mammals may avoid being harmed by plant toxins as follows:
the ability to neutralise toxins, e.g. with neutralising proteins
cautious sampling to determine whether a plant will have negative effects
What are examples of chemical adaptations in predators?
Chemical adaptations in predators include:
snakes, scorpions and spiders can produce venoms
chemical mimicry may be used to attract prey animals
chemical crypsis, or scent camouflage, allows ambush predators to lie in wait for prey without being detected
What are examples of physical adaptations that help predators to catch prey?
Examples of physical adaptations in predators include:
long-distance vision
eyes of predators located in the fronts of their skulls, giving good distance perception
the ability to detect chemicals released by prey animals, e.g. a good sense of smell
echolocation in bats
the ability to move at high speed, e.g. being adapted to run or swim fast
large canine teeth to catch and hold onto prey
Some species of snake may lie in wait for their prey for many weeks.
What type of predator adaptation is this?
Lying in wait for prey is an example of a behavioural adaptation in predators.
What are examples of chemical adaptations found in prey animals?
Examples of chemical adaptations in prey include:
toxins that deter predators, e.g. poison dart frogs and skunks
scent camouflage that allow prey to avoid detection
Prey animals always have eyes positioned on the sides of their heads.
What type of prey adaptation is this?
Eyes positioned in the sides of the head is an example of a physical adaptation in prey.
What are examples of behavioural adaptations found in prey animals?
Behavioural adaptations in prey animals include:
hiding
moving away from predators
living in a large group
playing dead
pretending to be larger than reality
What are some examples of plant adaptations for harvesting light?
Plant adaptations for harvesting light include:
trees that grow tall to reach the canopy
using other plants as a support to reach the canopy, e.g. lianas, epiphytes and
strangler epiphytes
being shade-tolerant
How do strangler epiphytes differ from lianas?
Strangler epiphytes begin their life in the canopy and grow both upwards and downwards to access resources, unlike lianas that germinate on the forest floor.
True or False?
Shade-tolerant plants contain the same photosynthetic pigments as plants in the canopy.
False.
Shade-tolerant plants often contain different photosynthetic pigments to absorb the limited light wavelengths that reach the forest floor.
Why do ground-dwelling forest plants often have large leaves?
Ground-dwelling plants have large leaves to maximise the surface area available for light absorption in the low-light conditions of the forest floor.
What is the difference between a species' fundamental niche and its realised niche?
The fundamental niche of a species is the niche that it has the potential to fill, based on its adaptations and tolerance limits, while the realised niche is the niche that a species actually fills in reality, when in competition with other species.
Define the term competitive exclusion in the context of ecological niches.
Competitive exclusion is the elimination of a competing species from its niche.
True or False?
When two species compete for the same niche, one of the two species will always become locally extinct.
False.
Competition for the same niche can lead to local extinction for the outcompeted species, but this is not the only outcome.
What are the possible outcomes of competitive exclusion for species?
Possible outcomes of competitive exclusion include:
one species becoming locally extinct
one species being forced into a slightly different niche
both competitors being forced into a smaller part of their fundamental niche